Our directory of things of interest

University Directory

Horseshoe crabs: blood in the water

Horseshoe crabs: blood in the water
15 Sep
2018
The demand for horseshoe crab blood – vital for testing new medical developments – is threatening the future survival of the species

If you want to test a new vaccine, heart valve or intravenous drug, you need a horseshoe crab, or, specifically, you need horseshoe crab blood. The bizarrely light blue vascular fluids of these curious marine creatures are packed with amebocytes, cells which produce an almost instantaneous defensive reaction to toxins, making them perfect for trialling new medical developments under the so-called LAL (Limulus amebocyte lysate) test. Consequentially, over half a million horseshoe crabs are plucked from their native habitats around the North American Atlantic coast every year (559,903 in 2015), each one ‘bled’ of up to 400ml of blood before being returned to the ocean (significantly far enough away from where they are initially harvested to limit the chances of animals being bled repeatedly).

horseshoe2The bleeding of horseshoe crabs is seen as vital for medicinal research (Image: Alamy)

The survival of the horseshoe crab is now threatened by this harvesting process. Somewhere between ten and 30 per cent of the animals die as part of the process, partially through blood loss, but primarily as a result of stress, high temperatures, accidental damage caused by being handled, or by developing hypoxia from spending significant periods of time out of the water. The Atlantic States Marine Fisheries Commission sets a maximum harvest mortality limit of 57,500 crabs per annum, but this figure is regularly exceeded. Furthermore, harvesting during spawning season makes it especially hard for the species to repopulate. The overall impact has been dramatic, with some coastal areas seeing horseshoe crab populations crashing, in the most extreme cases, by as much as 95 per cent over 15 years.

‘The gradual extinction of this once-abundant important species is alarming, and evidence shows many migrating bird populations have been declining in tandem with diminishing horseshoe crab populations,’ says Dr Anthony Dellinger from the University of North Carolina at Greensboro. ‘We wanted to find out the scope of the problem and begin to assess alternatives to current harvesting procedures.’ Farming captive horseshoe crabs could reduce the need for wild harvesting of the species, and make the whole LAL testing process more sustainable, explains Dellinger, while some researchers maintain hopes of even substituting a synthetic solution that requires no harvesting of the crabs at all. Nevertheless, separate threats, including climate change, habitat destruction, and the use of horseshoe crabs as eel and whelk fishing bait, look set to heap further pressure on this strange but vital species.

This was published in the September 2018 edition of Geographical magazine

geo line break v3

Free eBooks - Geographical Newsletter

Get the best of Geographical delivered straight to your inbox by signing up to our weekly newsletter and get a free collection of eBooks!

geo line break v3

Related items

Subscribe to Geographical!

geo line break v3

Free eBooks - Geographical Newsletter

Sign up for our weekly newsletter today and get a FREE eBook collection!

geo line break v3

University of Winchester

geo line break v3

EDUCATION PARTNERS

Aberystwyth University University of Greenwich The University of Derby

TRAVEL PARTNERS

Ponant

Silversea

Travel the Unknown

DOSSIERS

Like longer reads? Try our in-depth dossiers that provide a comprehensive view of each topic

MORE DOSSIERS

NEVER MISS A STORY - Follow Geographical on Social

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in NATURE...

Wildlife

A tightening of restrictions on the insecticides known as neonicotinoids…

Wildlife

Bonnethead sharks, the second smallest member of the hammerhead family,…

Nature

There’s more than enough plastic in the world. That’s why,…

Wildlife

The recent discovery of more than 200 million termite mounds…

Geophoto

The new year still remains a popular time to set…

Wildlife

After decades battling environmental crises that threaten to rob the…

Climate

As another new year beckons and the fight to protect…

Geophoto

A half century has passed since the ‘Earthrise’ photograph – widely believed to have…

Wildlife

Are howler monkeys being adversely affected by ingestion of pesticides containing…

Tectonics

Why unprepared tourists are putting themselves at risk in order…

Geophoto

The majestic and mighty polar bear is in danger of…

Wildlife

Exciting news for wildlife and photography enthusiasts alike – the…

Wildlife

A new system of robotic aerial vehicles is revolutionising the…

Wildlife

Technology used in creating safe urban environments is now being…

Climate

Brazil’s shift to the right of the political spectrum could…

Wildlife

Laura Cole travels to Orkney to find out why numbers…

Wildlife

The unprecedented frequency of winter tick epidemics have resulted in…

Oceans

Ocean debris, mostly composed of plastic, reaches remote Atlantic islands…

Geophoto

With motion detectors becoming ever more sophisticated, and clearer, crisper…

Nature

Natural capital is a way to quantify the value of…